Back when the Senate’s Gang of Eight was haggling over the details of its immigration-reform bill, TIME dug into four major hurdles the bill would have to clear. But now the dynamics have changed. The gang has published its proposal, and the details are now being debated in public. With the legislation now headed for mark up in the Judiciary Committee on May 9, here are four new obstacles around which supporters will have to navigate:

Problem #1: Stalling tactics from the right

In the Senate, conservatives opposed to the Gang of Eight’s bill have settled on a simple strategy: stall. The bill, detractors complain, is too big and too important to be crafted by an eight-man panel. A passel of conservatives have called for more hearings, more transparency, more opportunities to tweak the legislation to their liking. Even Rand Paul, who embraced immigration reform just a month ago, pulled a quick U-turn in the aftermath of the Boston bombing, urging the Senate to delay the bill while the investigation into the marathon plot plays out.

Conservatives in the House—where a separate bipartisan gang of negotiators still plans to drop its own template—have taken a different tack, insisting that the legislation be considered in smaller pieces rather than one massive (844-page) bill. That’s a nonstarter for the bill’s advocates. While John McCain and Chuck Schumer say they hope to garner support from a majority of both parties in the Senate, even members of the Gang concede that threading the legislation through the Republican-controlled House is going to be tricky. “The bill that’s in place right now probably can’t pass the House. It will have to be adjusted,” Senator Marco Rubio said this week.

Problem #2: Pushback from the left

The majority of Democrats have found plenty to like in the bill. But there’s still a chance that the political left could derail its passage. Immigrants’ rights groups held a conference call this week to vent concerns about the bill. Among their gripes: the 13-year path to citizenship is too long, its requirements too onerous, and a large swath of the undocumented population — included all immigrants who arrived in the U.S. illegally after 2011 — would be excluded.

Meanwhile, gay-rights advocates are unhappy that same-sex couples aren’t granted greater protections. According to Politico, Judiciary Committee Chairman Patrick Leahy, a Vermont Democrat, plans to introduce an amendment during the markup process that would allow gay Americans to sponsor their same-sex partners for green cards. That provision was excluded from the Gang of Eight’s framework because it is anathema not just to Republicans who might otherwise support the bill but also to influential religious groups who back the existing compromise. The amendment seems set to pass the committee, where a simple majority is required, but could hamper the bill’s prospects when it reaches the floor.

Problem #3: The cost for taxpayers

The nonpartisan Congressional Budget Office has yet to score the Senate bill. (On Thursday, it released an explanation of how it will do so on its website.) But conservatives will tout the hefty price tag as a reason to vote no. The Heritage Foundation, an influential conservative think tank, plans to release an analysis of the bill’s costs as soon as next week. In an interview with CNBC, the group’s president, former conservative senator Jim DeMint, offered a likely preview of the argument the report will make, citing “trillions of dollars of costs when [legalized immigrants] reach retirement age, get on Medicare, Social Security. These programs are already broke. Our country is already $17 trillion in debt. This will be a net loss, a huge cost to taxpayers. And it’s not fair to the 4 million people waiting around the world to come here legally.”

Problem #4: The conservative media storyline

Much of the conservative political establishment has rallied around immigration reform as a sheer political imperative. Not so the conservative media establishment. National Review, normally something of an antidote to the right-wing Internet fever swamps, has gone all-in against the bill, trying to fracture the fragile Gang by applying political pressure on Rubio. Check out their new cover, or this column dubbing Rubio Schumer’s “waterboy,” or this one arguing he was outmaneuvered.

None of this means the bill is bound to fail. But passing legislation of this scope is extremely difficult in an environment where the Republicans are determined the deny the President a political win. “It’s useful to stand back and remember that eight months ago, the official position of the Republican Party on immigration reform was self-deportation. There was not a single leading Republican who was advocating for comprehensive immigration reform. Quite a lot has changed since then,” White House Press Secretary Jay Carney told reporters Thursday. The President, he added, “hopes that progress will continue and we will see a bill emerge from committee and then from the Senate that has broad bipartisan support, and then, eventually, emerges from Congress in a form that he can sign. And that would be a major accomplishment. But obviously, there are hurdles to clear.”